The present invention relates to a method for maintaining a magnetic recording and reproducing device and a magnetic head, which method enables prevention of failure resulting from wear and dirt of a magnetic head and a library device which includes a container for storing many cartridges, each for holding a reel around which a magnetic recording medium (magnetic tape) is wound.
The magnetic recording and reproducing device for recording or reproducing information on a magnetic recording medium through a magnetic head has conventionally suffered from some shortcomings such as lowering of a signal-to-noise (S/N) ratio or reliability of the recording and reproducing systems resulting from dirt or wear of the magnetic head.
To overcome the shortcoming of dirt, there has been conventionally used a method in which a cleaning tape is moved in contact with the magnetic head for removing dirt of the head or in which a cleaning liquid is directly adapted to the magnetic head. To overcome the shortcoming of wear, replacement of the wear-out magnetic head is the only way. However, various techniques have been proposed for grasping when the head is to be replaced, that is, sensing an amount of wear of the magnetic head. For example, JP-B-4-19604 (JP-A-59-193519) published in Mar. 2, 1992 discloses a technique of sensing an amount of wear based on change of impedance of a magnetic head according to reduction of a sectional area of a gap part of a magnetic head core.
By the way, it is likely that a typical information device is concentratively managed from a remote place according to increase of an amount of information to be processed. Such a remote control operation is requested to be automatically operated without any maintenance operator. Under this circumstance, the reliability of a device itself is required to be enhanced in place of no maintenance operator. Further, if failure takes place in the device, it is desirous for the device to automatically recover the failed function. Alternatively, by presuming a possibility of occurrence of failure and issuing a warning before actual occurrence of failure, it is necessary to repair the device before the device is made inoperative.
As a representative example, a magnetic tape library device may be referred. The magnetic tape library device is a device arranged to automatically store as numerous magnetic tape (MT) cartridges as about 500 to 7000, selectively pick up one of these cartridges with a robot, set the picked cartridge to a magnetic tape device composing a recording and reproducing device, and return the magnetic tape to the original storage place after it is reproduced with the robot. This type of magnetic tape library device may be used for backing up a magnetic disk device whose volume is likely to be larger or for a broadcasting business. The library device is arranged to hold about 4 to 40 magnetic tape devices and at least two robots. It implements substantially complete automatic exchange and storage of a magnetic tape. In this kind of magnetic tape device, failure resulting from wear or dirt of a magnetic head remarkably lowers the reliability of the device. The wear of the magnetic head lowers a reproduced output voltage level in a long-term range, finally causing the magnetic head itself to be unserviceable. The time from a first use start to the time when the head becomes unserviceable is called a life of a head. In this case, it is necessary to replace the magnetic head. In the circumstances where the magnetic tape device is remotely operated by a computer, it is necessary to exactly grasp when the head is to be replaced. The wear of the magnetic head lowers a reproduced output. This lowering takes place at a shorter period than the life of a head, that is, frequently. To overcome dirt of the magnetic head, as mentioned above, the head cleaning is executed. From a viewpoint of simplifying the remote operation and the maintenance, the magnetic tape library is required to automatically execute the head cleaning operation if necessary. On the other hand, the conventional technique needs a maintenance operator to determine the state of the magnetic head with his or her eyes and when the head is replaced or cleaned according to the determined state. It means that the conventional technique cannot cope with the remote-control management and the automated function recovery of the magnetic tape library device.